Within the meaning of the invention, orientation information is understood to mean in particular auxiliary geometries which are superimposed on an observation image in surgical microscopes. With such auxiliary geometries it is possible, for example, to facilitate orientation in an operating area for an operator. For example, with such auxiliary geometries, tissue and bone structures in an operating area can be indicated precisely to an operator. Orientation information within the meaning of the invention can, however, also consist in images which are recorded preoperatively on a patient using diagnostic apparatuses such as MRT (Magnetic Resonance Tomography) or MRI (Magnetic Resonance Imaging) apparatuses, for example, and which show the structures in an operating area which cannot be identified or can only be identified with difficulty by an observer in the observation image of an object region.
In this case, a module is understood to mean both an assembly which is permanently integrated in a visualization apparatus and an assembly which is designed for replaceable supplementation or retrofitting of a visualization device and which can be connected to a basic body of a visualization device, for example using dovetail couplings.
A visualization apparatus comprising a module of the type mentioned at the outset is known from WO 2013/072422 A1. The document describes a visualization apparatus in the form of a surgical microscope which has an imaging optical unit which generates an observation image of an object plane. This surgical microscope is an eye surgery microscopy system. It contains an electronic image sensor, which is connected to a computer unit for calculating the position and orientation of a patient's eye by means of image analysis. Thus, orientation information in the form of a calculated auxiliary geometry which is superimposed, in correlated form, on the observation image of a patient's eye can be displayed to an observer.
In order to enable precise orientation within an operating area for an operator, it is necessary for the superimposed orientation information displayed to be aligned precisely with respect to the observation image in such a visualization apparatus.
The computer unit of the visualization apparatus described in WO 2013/072422 A1 contains a computer program for this purpose, which computer program enables compensation for determined errors during acquisition of the image data on which the digitally generated images are based and matching of image data to determined position, orientation and scaling errors.
DE 101 57 613 A1 discloses a visualization apparatus in which the image of a display can be provided both in the optical channel of an optical observation beam path and on an image sensor for acquiring an object region image in the corresponding observation beam path. In the case of the display of display information in the observation beam path by means of the display, the display information is in this case always supplied to the image sensor.